Groundwater Lowering in Construction

Cashman, Pat M.; Preene, Martin

doi:10.1201/9781003050025

Cited by 14 publications

(9 citation statements)

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“…The coefficient of permeability for silty clay/clayey silt was 1x10 -10 m/s. The coefficient of permeability for silty fine sand was from 1×10 -5 to 1×10 -7 m/s [27][28][29][30][31][32][33].…”

Section: Methodsmentioning

confidence: 99%

Numerical Analysis of Settlement of a Piled Raft Foundation on Coastal Soil

et al. 2023

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There is a growing demand for multi-story buildings for residence and commercial purposes in coastal areas of Sindh, Pakistan. Such types of soils are generally considered more compressible with high groundwater levels, which may cause lower shear strength and higher settlement. The computation of the settlement of foundations requires the use of advanced constitutive models, which are not commonly used due to a lack of field or experimental data. This study is carried out to illustrate the use of an advanced soil model, i.e., Hardening Soil Model for the computation of settlement. For this purpose, numerical modeling was carried out using Finite Element Program PLAXIS 2D. Initially, the MC Model was utilized for the calculation of the settlement of a 10-story building in the coastal soil. In addition, parametric analyses for the effects of modulus of elasticity, permeability, and dilatancy angle were carried out. The results mainly suggest that the settlement of the building constructed on a piled raft foundation, predicted with the MC model, was 40% higher than that of the HS model. For prediction of settlement of the piled raft foundation, the results suggest that the HS model can be given preference as compared to the MC model. Doi: 10.28991/CEJ-2023-09-02-05 Full Text: PDF

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Section: Methodsmentioning

confidence: 99%

Numerical Analysis of Settlement of a Piled Raft Foundation on Coastal Soil

et al. 2023

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“…The impact produced outside the excavation by the lowering of the piezometric head must be also considered when designing a dewatering system. The induced drawdown to ensure working conditions must not be excessive to minimize outer impacts such as (i) the loss of hydraulic resources, and (ii) soil settlements [17].…”

Section: Dewatering Systemmentioning

confidence: 99%

“…V is lower than 0, the soil completely loses its shear strength and starts to behave like a fluid. Bottom uplift may occur when the excavation bottom is located above a confined aquifer whose P W is not enough reduced [17]. Liquefaction and bottom uplift may also produce the deformation of the soil outside the excavation since the soil may migrate towards the centre of the excavation when they occur.…”

Section: Bottom Stabilitymentioning

confidence: 99%

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Underground Excavations Below the Water Table by the Cut-and-Cover Method

Pujades¹,

Jing²,

Lu³

et al. 2023

Civil Engineering

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Most underground constructions, which are needed to improve mobility and increase available space in urban areas, require excavations that are usually deeper than the water table (e.g., for the construction of stations or underground parking lots). A frequently used technique to develop excavations under these conditions consists in combining the cut-and-cover method with a dewatering system based on deep pumping wells. Retaining walls used for the cut-and-cover method allow excavating between vertical walls and minimizes the inflow of groundwater, while deep pumping wells provide dry and stable conditions. Despite this technique is widely used, some aspects related with the presence of groundwater must be considered to avoid accidents. Dewatering systems must be properly designed to guarantee suitable conditions and to minimize the pumping settlements outside of the working area. In addition, it is required to assess the presence of defects in the retaining walls because the flow of groundwater through them may entail negative consequences. This chapter explains procedures (i) to design efficient dewatering systems considering the working conditions, the stability and the impacts generated in the vicinity of the construction, and (ii) to evaluate the state of the retaining walls by using hydrogeological tools.

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“…The water level outside the retaining wall actually falls during construction, which results in "unconfined flow" where the upstream profile becomes another unknown to be solved. In fact, ground water control is an important issue for deep excavation analysis, and many methods have been developed to control the ground water during excavation [27][28][29]. For Cheng's past experience, recharge wells outside the retaining wall have been used to restore the water table for the Sheung Wan and Wanchai MTR Concourses in Hong Kong.…”

Section: Unconfined Flowmentioning

confidence: 99%

Seepage Analysis for Construction, with Applications to Some Projects in Hong Kong

Cheng

Zhu

et al. 2021

Geofluids

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Deep excavations are intensively carried out in many cities in China and other countries. One of the major loadings in such construction work is the water pressure, and great effort is required to assess the seepage problem and the corresponding water pressure on the retaining wall for a good design and construction. Different methods used for the seepage analysis are discussed in this paper through a series of projects in Hong Kong. Some interesting phenomena from the seepage analysis will also be discussed. Two large scale seepage field tests in Hong Kong are also used for the illustration of the back analysis in seepage problems which are seldom carried out. The comparative studies demonstrate that a realistic seepage analysis is very important for deep excavation works, but it was not seriously considered in the past.

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Groundwater Lowering in Construction

Cited by 14 publications

References 0 publications

Numerical Analysis of Settlement of a Piled Raft Foundation on Coastal Soil

Numerical Analysis of Settlement of a Piled Raft Foundation on Coastal Soil

Underground Excavations Below the Water Table by the Cut-and-Cover Method

Seepage Analysis for Construction, with Applications to Some Projects in Hong Kong

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